Pi is what's known as an irrational number, which means that its decimal representation is both infinite and non-repeating.

We've been using computers to calculate the digits of Pi for decades. In 1949, John von Neumann and his colleagues used ENIAC — the world's first general-purpose electronic computer — to calculate Pi to the 2,037th digit. We surpassed the million-digit milestone in 1973. And on October 17, 2011, after 371 days of computing, Shigeru Kondo finished calculating Pi to 10 trillion decimal places.

The picture up top is adapted from a rather simple but effective piece of data visualization, created by the folks at design studio TWO-N, which represents the first four-million digits of Pi in a brilliant mess of interactive pointillism.

Each digit, from 0-9, was assigned a color based on the legend pictured here, and then rendered as a single, 1x1 pixel. Line the pixels up in the order designated by Pi, confine them to a 4-millon pixel image, and you get this interactive applet here, which lets you soar around the entire image, inspecting 500,000-digit sections at a clip. There's even an interesting search function that lets you probe the mathematical mosaic for number up to eight digits in length. [TWO-N via information aesthetics]